United States Pat. No. 4,216,741, granted Aug. 12, 1980, to Owen R. Moss and assigned to Hazleton Systems, Inc. discloses a chamber of the type mentioned above in which the catch pans of animal exposure chambers are converted from obstacles to the uniform distribution of gas within the chamber into instruments for its attainment. In this chamber, two "stacks" of trays are spaced from the walls of the chamber and spaced apart along a mid-plane of the chamber to provide spaces for the downward flow of gas between pans. In this arrangement vortices are produced between each pair of pans which result in uniform mixing of the gas or aerosol.
Exposure chambers of the type described in the Moss patent have been widely adopted and have proven very successful. They have been marketed commercially in a standardized size which is that described in the patent, that is to say, 50 inches (127 cm) wide by 49 inches (124.5 cm) deep by 6 feet 10 inches (208.3 cm) high, with an animal caging and exposure section 49 inches (124.5 cm) high. Six catch pans, 23 inches (58.4 cm) total width by 47 inches (119 cm) total length, in two vertical columns, are provided within the chamber.
It would be highly desirable to have a chamber of approximately half the width given above so that it could pass the usual doors. It would also be desirable for the pans and cages to be of the same size as those in the chamber described in the patent so that they would be interchangeable. The object of the present invention is to provide a chamber meeting the above requirements which still produces the uniform mixing obtained in the chamber described in the patent.